Devices for opening doors have been well established commercially for many years. They are most commonly employed for use by handicapped people and commonly include some form of actuator secured to the structure surrounding the door and suitable controls positioned so that someone in a wheelchair can energize the system conveniently. The door-opening mechanism is usually associated with some form of door closer, with the two systems occasionally being integrated into one device. In either case, these units have usually been mounted on the structure above the door that joins the two door jambs, which is commonly referred to as the header. In the design of modern buildings, the header structure is frequently reduced to a very small vertical dimension or eliminated entirely so that the door extends all the way to the ceiling. Obviously, this presents a problem in the mounting of conventional door-opening equipment.
The actuating mechanism of a conventional door opener usually consists of some form of electric motor, the main function of which is to generate torque in a shaft carrying a radius arm that extends out over the door. Force is transferred to the door usually through the use of a link pivoted at one end to the end of the radius arm, and at the other end to a suitable bracket secured to the door. This arrangement presents some problems in installation, particularly if it becomes necessary to accommodate unknown interior structure of the door for a suitable location for the bracket fastenings. The pivoted link arrangement also requires that attention be given to the adjustment of the length of the link and the placement of the bracket so that the pivot connection with the radius arm does not pass "over center", and interfere with the operation of the mechanism. Also, with a linkage mechanism, if the door is also to be operated manually, the linkage and door opener are forced to travel even when the door is operated manually.